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Rhizoma Coptidis, a traditional herb medicine, has been used in Korea and China for many centuries as a treatment for many disease. The purpose of the present study was to determine the effect of Rhizoma Coptidis on histamine-induced tracheal smooth muscle contraction in guinea pigs and rats. Guinea pigs(500g, male) and rats(250g, male) were killed by exposure and a segment (8-10mm) of the thoracic trachea from each guinea pig was cut into equal segments and mounted ’in pairs’ in a tissue bath. Contractile force was measured with force displacement transducers under 0.5g loading tension. The dose of histamine which evoked 50% of maximal response () was obtained from cumulative dose response curves for histamine (). Contractions evoked by histamine() were inhibited significantly by Rhizoma Coptidis. The mean percent inhibition was 33.2% after 1.5mg/ml Rhizoma Coptidis, and 69.5% after 5.0mg/ml Rhizoma Coptidis in guinea pigs, and the mean percent inhibition was 25.3% after 1.5mg/ml Rhizoma Coptidis, and 65.8% after 5.0mg/ml Rhizoma Coptidis in rats. Indomethacin () slightly but significantly attenuated the inhibitory effects of Rhizoma Coptidis. But propranolol and methylene blue () did not significantly alter the inhibitory effect of Rhizoma Coptidis. These results indicate that Rhizoma Coptidis can relax histamine-induced contraction of guinea pig and rat tracheal smooth muscle, and that this inhibition involves, in part, cyclooxygenese inhibitor.
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